Guleda Onkal Engin

The effect of transient loading on the performance of a mesophilic anaerobic contact reactor at constant feed strength

Anaerobic contact reactor is a high rate anaerobic process consisting of an agitated reactor and a solids settling tank for recycling. It was proved earlier that this type of reactor design offers highly efficient performance in the conversion of organic matter to biogas. In this study, the effect of transient loading on reactor performance in terms of a number of key intermediates and parameters such as, COD removal, pH and alkalinity change, VFAs, effluent MLSS concentration and biogas efficiency over time was examined. For this purpose, a step increase of organic loading rate from 3.35kg COD/m(3)day to 15.61kg COD/m(3)day was employed. The hydraulic retention time decreased to a value of 8.42h by an increase in the influent flow-rate during the transient loading. It was observed that the mesophilic anaerobic contact reactor (MACR) was quite resistant to large transient shocks. The reactor recovered back to its baseline performance only in 15h after the shock loading was stopped. Hence, it can be concluded that this type of reactor design has a high potential in treating food processing wastewaters with varying flow characteristics.

Effect of carbon to nitrogen ratio of feed wastewater and sludge retention time on activated sludge in a submerged membrane bioreactor

This paper investigated the effects of extracellular polymeric substances (EPS) on the activated sludge rheology in a submerged membrane bioreactor (sMBR) operated at different sludge retention time (SRT) values and different carbon to nitrogen ratios (C/N) of feed wastewater. The C/N ratios of the feed were adjusted accordingly so that synthetic wastewaters prepared simulated municipal wastewater, non-toxic wastewater with high C/N ratio and non-toxic wastewater with low C/N ratio. A number of important operational parameters such as mixed liquor suspended solid (MLSS), protein fraction of EPS (EPSp), carbohydrate fraction of EPS (EPSc), protein fraction of soluble microbial product (SMPp), carbohydrate fraction of SMP (SMPc), apparent viscosity, critical flux and hydrophobicity in mixed liquor and their correlations were investigated in the sMBR systems operated. The statistical analysis indicated that the C/N ratio of feed, SRT, MLSS and SMPc were found to have positive effects on apparent viscosity at three different shear rates. On the other hand, a negative impact was detected between the apparent viscosities and the critical fluxes. It was also observed that there is a significant positive correlation between hydrophobicity and both EPSp and SMPp.

Development of a sensitive liquid–liquid extraction method for the determination of N-butyryl-L-homoserine lactone produced in a submerged membrane bioreactor by gas chromatography mass spectrometry and deuterated anthracene as the internal standard

Quorum sensing is defined as the bacterial communication through sending and receiving chemical signals such as N-acyl homoserine lactone (AHL) and oligopeptide for Gram negative bacteria and Gram positive bacteria, respectively. This mysterious bacterial interaction regulates a wide range of activities affecting the environment, agriculture, and therefore, humans. In the last century, quorum sensing investigations trying to follow and measure these chemical signals have accelerated. In this study, an analytical method was developed and optimized in order to extract and measure one of the AHLs: N-butyryl-L-homoserine lactone (C4-HSL) by gas chromatography-mass spectrometry (GC-MS). The aim of the study was to develop a method that increases the sensitivity and precision of AHL detection by GC-MS due to the problem in the determination of analytes in wastewater which have a complex matrix. The limits of detection and quantification obtained for C4-HSL were 12.9 ng mL−1 and 43.3 ng mL−1, respectively. The precision of the method was improved upon using deuterated anthracene as the internal standard, which gave a lower relative standard deviation compared to that without the internal standard.

Activated sludge properties in a submerged membrane bioreactor: effect of COD/TKN ratio of wastewater

The properties of activated sludge are very important in a membrane bioreactor (MBR) in terms of membrane fouling. The most important parameters affecting the membrane fouling can be listed as mixed liquor suspended solid (MLSS) concentration, soluble microbial products (SMPs), extracellular polymeric substances (EPSs), floc size, aeration and viscosity of both supernatant and activated sludge. The COD/TKN ratio also affects the physical properties of sludge in MBR system. This study aimed to investigate the effect of chemical oxygen demand-to-total Kjeldahl nitrogen (COD/TKN) ratio of feed wastewater treated in an MBR on biological components of activated sludge. The activated sludge characteristics were determined by quantitative analyses such as MLSS, EPS, SMP, floc size distribution, zeta potential, relative hydrophobicity and capillary suction time in a submerged MBR treating simulated wastewater having different COD/TKN ratios (16, 56 and 107). The COD and TKN removal efficiencies were found to be almost equal in the sMBRs having different COD/TKN ratios. However, it was seen that the EPS content and SMP concentration in the supernatant increased with increasing COD/TKN ratio. The results indicated that the COD/TKN ratio of feed should be considered as an effective parameter on activated sludge properties in sMBR systems.

Performance and activated sludge characteristics at short solid retention time in a submerged MBR: effects of C/N ratio of wastewater

ABSTRACT This study investigated the effect of carbon to nitrogen (C/N) ratio of influent wastewater on performance and activated sludge properties at a sludge retention time of 5 d in a submerged membrane bioreactor. The chemical oxygen demand and ammonia–Nitrogen (NH3–N) removal efficiencies were found to be over 96.3% and 86.9% in the sMBRs having different C/N ratios. It was found that total extracellular polymeric substances and total soluble microbial products increased with an increase in C/N ratio. It was also observed that critical flux, relative hydrophobicity and zeta potential values decreased, and capillary suction time, particle size and viscosity of sludge increased as the C/N ratio increased.This study investigated the effect of carbon to nitrogen (C/N) ratio of influent wastewater on performance and activated sludge properties at a sludge retention time of 5 d in a submerged membrane ...

Optimization of paper mill industry wastewater treatment by electrocoagulation and electro-Fenton processes using response surface methodology

This study deals with chemical oxygen demand (COD), phenol and Ca+2 removal from paper mill industry wastewater by electrocoagulation (EC) and electro-Fenton (EF) processes. A response surface methodology (RSM) approach was employed to evaluate the effects and interactions of the process variables and to optimize the performance of both processes. Significant quadratic polynomial models were obtained (R2 = 0.959, R2 = 0.993 and R2 = 0.969 for COD, phenol and Ca+2 removal, respectively, for EC and R2 = 0.936, R2 = 0.934 and R2 = 0.890 for COD, phenol and Ca+2 removal, respectively). Numerical optimization based on desirability function was employed; in a 27.55 min trial, 34.7% of COD removal was achieved at pH 9 and current density 96 mA/cm2 for EC, whereas in a 30 min trial, 74.31% of COD removal was achieved at pH 2 and current density 96 mA/cm2 and H2O2/COD molar ratio 2.0 for EF. The operating costs were calculated to be 6.44 €/m3 for EC and 7.02 €/m3 for EF depending on energy and electrode consumption at optimum conditions. The results indicate that the RSM is suitable for the design and optimization of both of the processes. However, EF process was a more effective technology for paper mill industry wastewater treatment as compared with EC.

The investigation of paper mill industry wastewater treatment and activated sludge properties in a submerged membrane bioreactor

The paper mill industry produces high amounts of wastewater and, for this reason, stringent discharge limits are applied for sustainable reclamation and reuse of paper mill industry wastewater in many countries. Submerged membrane bioreactor (sMBR) systems can create new opportunities to eliminate dissolved substances present in paper mill wastewater including. In this study, a sMBR was operated for the treatment of paper mill industry wastewater at 35 h of hydraulic retention time (HRT) and 40 d of sludge retention time (SRT). The chemical oxygen demand (COD), NH3-N and total phosphorus (TP) removal efficiencies were found to be 98%, 92.99% and 96.36%. The results demonstrated that sMBR was a suitable treatment for the removal of organic matter and nutrients for treating paper mill wastewater except for the problem of calcium accumulation. During the experimental studies, it was noted that the inorganic fraction of the sludge increased as a result of calcium accumulation in the reactor and increased membrane fouling was observed on the membrane surface due to the calcification problem encountered. The properties of the sludge, such as extracellular polymeric substances (EPS) and soluble microbial products (SMP), relative hydrophobicity, zeta potential and floc size distribution were also monitored. According to the obtained results, the total EPS was found to be 43.93 mg/gMLSS and the average total SMP rejection by the membrane was determined as 66.2%.

Strength and durability characterization of pelletized coal–biomass household briquettes

ABSTRACT Increase in waste sludge disposal is always seen as a problem from the point of production industry. However, it is clear that the reuse and recycle of sewage sludge could be a serious economic input. The most important action should be to determine the sludge characterizations and direct the producers towards appropriate reuse and recycling opportunities. In this study, reuse method was examined to produce coal briquette, which will constitute an example for waste sludge. In order to make use of the waste sludge, five different coal briquette samples were produced by mixing powdered coal and bitumen together with waste sludge, at different ratios. The overall results indicated that the sample named CB3 having 70% powdered coal, 20% waste sludge, and 10% bitumen was found to be the optimum coal briquette among the other samples produced. The proximate analysis of the optimum briquette sample was carried out according to the Turkish standards and regulations and it was found out that the produced briquette coal can have commercial value with a gross calorific value of 30.03 MJ/kg and 7.30% ash content.